Si Substrate Effect on Characteristics of Solid State Incandescent Light Emitting Devices

Abstract

In the solid state light emitting device (LED), the single wavelength light is emitted from the pn junction structure made on a compound semiconductor wafer [1]. A novel solid-state incandescent light emitting device (SSI-LED) that is made from the MOS capacitor with a high-k gate dielectric was reported recently [1-5]. It emits the warm white light based on the principle of thermal excitation of nano-resistors formed from the dielectric breakdown process [2,5]. This kind of device can be used in lighting, on-chip optical interconnect, nonvolatile memories, etc. [6-8]. In this study, authors report the Si substrate effect on the electrical and optical properties of the device before and after the formation of nano-resistors.MOS capacitors made of the ZrHfO high-k dielectric and ITO gate electrode were fabricated on the dilute HF cleaned Si (100) IC and the poly-Si solar wafers. The high-k dielectric layer was sputter deposited on the wafer followed by furnace annealing at >900oC for 3 min in O2. The sputter deposited ITO film was etched into gate electrodes with a HCl:HNO3=3:1 solution. An aluminum film was deposited on the backside of the wafer to form the ohmic contact. The complete sample was annealed at 400oC for 5 min under N2/H2 90%/10%. The capacitance-voltage (C-V) curve was measured with an Agilent 4284 meter based on which the EOT, VFB , Dit , and Qot were calculated. Subsequently, nano-resistors were formed after the dielectric breakdown process. Light emitted from the SSI-LED under a fixed Vg was characterized.Figure 1 shows C-V hysteresis curves of capacitors made on the (a) Si (100) IC wafer and (b) poly-Si solar wafer. They show similar EOT, Qot , and small hysteresis that means very few trapped charges [9]. However, the device on the poly-Si solar wafer has a much larger Dit than that on the Si (100) wafer, i.e., 1.4x1011 cm-2 eV-1 vs. 7.0x1010 cm-2eV-1, which means a larger interface state density in the former [10]. The small bump in the Fig. 1(b) curve corresponds to the existence of interface states [11]. The high interface states are related to the large number of active defects that lead to the large leakage current, large number of low-frequency noises, and low mobility [11]. The textured surface of the solar wafer could be the reason for the large interface states [12].Figure 2 shows the top views of light emission from SSI-LEDs prepared on the (a) Si (100) IC wafer and (b) poly-Si solar wafer at Vg = -20V. The bright dots in Fig. 2 correspond to thermally excited nano-resistors. They were more uniformly distributed in Fig. 2(a) than in Fig. 2(b). Fig. 2(b) shows many large bright dots, which are contributed by closely located nano-resistors [13]. The color difference among dots could be due to the temperature difference [14]. The higher the temperature is, the shorter the light wavelength is. More detailed electrical and optical characteristics on SSI-LEDs will be presented and discussed.1. S. Nakamura, T. Mukai, and M. Senoh, Appl. Phys. Lett., 64(13), 1687 (1994).2. Y. Kuo and C.-C. Lin, Appl. Phys. Lett., 102(3), 031117 (2013).3. Y. Kuo and C.-C. Lin, Electrochem. Solid-State Lett., 2(8), Q59 (2013).4. Y. Kuo and C.-C. Lin, Solid-State Electron., 89, 120 (2013).5. C.-C. Lin and Y. Kuo, Appl. Phys. Lett., 106(12), 121107 (2015).6. Y. Kuo, ECS Trans., 69(12), 23 (2015).7. S. Zhang and Y. Kuo, ECS J. Solid State Sci. Technol., 6(4), Q39 (2017).8. S. Zhang and Y. Kuo, ECS Trans., 75(45), 17 (2017).9. W. L. Leong, P. S. Lee, S. G. Mhaisalkar, T. P. Chen, and A. Dodabalapur, Appl. Phys. Lett., 90(4), 042906 (2007).10. M. Miczek, C. Mizue, T. Hashizume, and B. Adamowicz, J. Appl. Phys., 103(10), 104510 (2008).11. S. Hlali, N. Hizem, L. Militaru, A. Kalboussi, and A. Souifi, Microelectron. Reliab., 75, 154 (2017).12. L. A. Dobrzański, A. Drygala, J. Achiev. Mater. Manuf. Eng., 31(1), 77 (2008).13. A. Shukla and Y. Kuo, 239th ECS Meeting. Abst. 145365 (2021).14. A. Shukla and Y. Kuo, ECS J. Solid State Sci. Technol., 9(6), 065017 (2020). Figure 1